Claw hand tendon transfer

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claw hand tendon transfer procedures Zancolli lasso Brand FDS intrinsic replacement surgery

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https://pmc.ncbi.nlm.nih.gov/articles/PMC2741332

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claw hand tendon transfer Bouvier test static dynamic procedures donor motors insertion sites summary

Here is a comprehensive summary of tendon transfer surgery for claw hand deformity:

Claw Hand - Tendon Transfer

Pathomechanics

Claw hand results from intrinsic muscle paralysis (interossei + ulnar-innervated lumbricals to ring and little fingers), most commonly from ulnar nerve palsy (low or high). With intrinsics absent:

Extrinsic extensors (EDC) pull the MCP joints into hyperextension
Extrinsic flexors (FDP/FDS) flex the IP joints unopposed
This produces the classic "intrinsic minus" posture

Low ulnar palsy causes more dramatic clawing (FDP intact) than high ulnar palsy (FDP also paralyzed, so less PIP/DIP flexion force).

The "ulnar paradox": low lesions cause worse clawing than high lesions because FDP to ring/little fingers is intact.

Pre-operative Assessment: Bouvier's Test

This test determines whether clawing is simple or complex and guides choice of procedure.

How to perform: Passively block MCP hyperextension (hold MCP in slight flexion). Ask the patient to extend the IP joints.

Result	Interpretation	Implication
PIP/DIP extend fully (Positive test)	Simple clawing - extensor apparatus intact	Static OR dynamic procedures both possible
PIP/DIP remain flexed (Negative test)	Complex clawing - central slip/lateral bands attenuated	Dynamic tendon transfer mandatory (insertion into lateral band)

Goals of Tendon Transfer in Claw Hand

Correct MCP hyperextension (primary goal - restores the intrinsic-plus posture)
Extend the PIP and DIP joints via lateral band insertion (in complex clawing)
Integrate MCP flexion with IP extension (coordinated grasp)
Restore key pinch (adductor pollicis function)
Improve grip strength
Restore ring/little finger FDP flexion (in high ulnar palsy)

Classification of Procedures

A. STATIC Procedures (Bouvier positive only)

Prevent MCP hyperextension mechanically, rely on EDC for IP extension:

Procedure	Mechanism
MCP joint volar plate capsulodesis (Zancolli capsulodesis)	Distally based volar plate flap advanced proximally to metacarpal neck - limits MCP extension
Bony block on dorsum of metacarpal head (Mikhail)	Mechanical stop to MCP hyperextension
Pulley advancement / A1+A2 release (Bunnell)	Bowstringing of flexor tendons increases MCP flexion moment arm
Tenodesis to deep transverse metacarpal ligament	Passive tether preventing MCP extension

Static procedures can stretch out over time and recurrence of clawing may occur. Reserve for cases where donor tendons are unavailable.

B. DYNAMIC Procedures

Group 1: Superficialis (FDS) Transfers

Donor: FDS of middle or ring finger (split into 4 tails for all fingers, or individual slips)

Procedure	Route	Insertion	Notes
Modified Stiles-Bunnell	Volar to deep transverse metacarpal ligament, through lumbrical canal	Lateral band	Corrects complex clawing; risk of PIP hyperextension (swan neck) if joints are lax
Burkhalter modification	Same route	Proximal phalanx (instead of lateral band)	Prevents PIP hyperextension; adequate for simple clawing
Zancolli Lasso	FDS passed through A1 pulley	Sutured back onto itself around A1	Simple, reliable; prevents MCP hyperextension; IP extension only by EDC - suitable for Bouvier-positive claws

The Zancolli Lasso is the simplest. FDS of ring finger is divided distally, retrieved into the palm, split into 4 slips, each passed through respective A1 pulley and sutured back under tension. It does NOT restore IP extension via lateral band.

Drawbacks of FDS transfers:

Removal of FDS weakens grip (especially ring/little donor in ulnar palsy)
Swan neck deformity risk (with lateral band insertion)
FDS of ring finger may be the only functioning flexor in high ulnar palsy - cannot sacrifice it

Group 2: Wrist Motor Transfers (Brand/Riordan/Fowler type)

Donors: ECRL, ECRB, FCR, Brachioradialis (all require a free tendon graft extension)

Procedure	Donor	Route	Insertion
Brand transfer	ECRL or ECRB (with palmaris longus or plantaris graft, split into 4 tails)	Through intermetacarpal spaces (between 2nd-3rd MC), along lumbrical canal	Lateral band (corrects complex clawing) or proximal phalanx
Riordan	FCR with graft	Similar route	Lateral band
Fowler / Tsuge dynamic tenodesis	Tendon graft looped through extensor retinaculum at wrist	Along lumbrical canal	Lateral band

When wrist flexes, the Fowler/Tsuge tenodesis passively tightens and flexes the MCPs/extends IPs - a passive but elegant solution.

Advantages over FDS transfers:

Preserve FDS, maintain grip strength
ECRL/BR are expendable donors innervated by radial nerve
Can augment grip strength

Disadvantage:

Require a free tendon graft (2 surgeries or simultaneous harvest)
Adhesions in intermetacarpal space can severely limit excursion

Decision Algorithm

Claw hand
    ├── Bouvier's Test POSITIVE (simple clawing)
    │       ├── Static: Zancolli capsulodesis / pulley advancement
    │       └── Dynamic: Zancolli lasso, Burkhalter (proximal phalanx insertion)
    │
    └── Bouvier's Test NEGATIVE (complex clawing)
            └── Dynamic ONLY with LATERAL BAND insertion:
                    ├── Modified Stiles-Bunnell (FDS → lateral band)
                    └── Brand/ECRL transfer (with graft → lateral band)

Donor Selection Summary

Donor	Innervation	Needs Graft?	Best Use
FDS ring/middle	Median	No	Zancolli lasso, Stiles-Bunnell; avoid in high ulnar palsy (ring FDS may be only flexor)
ECRL	Radial	Yes (4-tail graft)	Brand transfer; expendable, good excursion
ECRB	Radial	Yes	Alternative wrist motor
FCR	Median	Yes	Riordan transfer
Brachioradialis	Radial	Yes	Alternative if ECRL/ECRB used elsewhere

Key Points for Exams

The Zancolli lasso is the most common static-equivalent simple procedure (dynamic in mechanism but prevents MCP extension only)
Bouvier's test negative = must insert into lateral band (not just proximal phalanx)
Low ulnar palsy = worse claw (ulnar paradox) because FDP ring/little intact
FDS transfers do not improve grip strength; wrist motor transfers (ECRL) can
Swan neck is the main complication of lateral band insertion with FDS transfer in lax joints
For combined median + ulnar palsy (all intrinsics lost), ECRL-based transfers are preferred as FDS donors are unavailable or median nerve motors are also lost

Sources: Tendon Transfers for Ulnar & Median Nerve Palsy, Outcomes of Tendon Transfer for Ulnar Claw Hand, Bouvier's Maneuver - ISSH, Campbell's Operative Orthopaedics 15th Ed 2026

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